Out of the box in Fedora 26 I see that our gtk3 version of LibreOffice mostly works under
broadway so here's libreoffice displaying through firefox. Toolbar is toast, but dialogs and menus work.
broadwayd :5 &
firefox http://127.0.0.1:8085 &
GDK_BACKEND=broadway BROADWAY_DISPLAY=:5 soffice --nologo &